CopyOnWriteArraySet的contains(E e)方法检查Set中是否存在给定元素。

用法:

public boolean contains(Object o)

参数：该函数接受单个强制参数，该参数指定要在Set中检查其外观的元素。

返回值：如果该元素存在，则该函数返回true，否则返回false。

以下示例程序旨在说明上述功能：

示例1:

// Java Program to illustrate the CopyOnWriteArraySet

// contains() method in Java

import java.util.concurrent.CopyOnWriteArraySet;

import java.util.*;

public class GFG {

public static void main(String[] args)

{

// create object of CopyOnWriteArraySet

CopyOnWriteArraySet ArrSet

= new CopyOnWriteArraySet();

// Add elements

ArrSet.add(32);

ArrSet.add(67);

ArrSet.add(67);

ArrSet.add(100);

// print CopyOnWriteArraySet

System.out.println("CopyOnWriteArraySet: "

+ ArrSet);

// check if 100 is present

// using contains() function

if (ArrSet.contains(100))

System.out.println("100 is "

+ "present in the Set");

else

System.out.println("100 is "

+ "not present in the Set");

// check if 20 is present

// using contains() function

if (ArrSet.contains(20))

System.out.println("20 is "

+ "present in the Set");

else

System.out.println("20 is "

+ "not present in the Set");

}

}

输出：

CopyOnWriteArraySet: [32, 67, 100]

100 is present in the Set

20 is not present in the Set

示例2:

// Java Program to illustrate the CopyOnWriteArraySet

// contains() method in Java

import java.util.concurrent.CopyOnWriteArraySet;

import java.util.*;

public class GFG {

public static void main(String[] args)

{

// create object of CopyOnWriteArraySet

CopyOnWriteArraySet ArrSet

= new CopyOnWriteArraySet();

// Add elements

ArrSet.add("geeks");

ArrSet.add("gfg");

ArrSet.add("jgec");

ArrSet.add("sudo");

// print CopyOnWriteArraySet

System.out.println("CopyOnWriteArraySet: "

+ ArrSet);

// check using contains() function

if (ArrSet.contains("gfg"))

System.out.println("gfg is "

+ "present in the Set");

else

System.out.println("gfg is "

+ "not present in the Set");

// check using contains() function

if (ArrSet.contains("best"))

System.out.println("best is "

+ "present in the Set");

else

System.out.println("best is "

+ "not present in the Set");

}

}

输出：

CopyOnWriteArraySet: [geeks, gfg, jgec, sudo]

gfg is present in the Set

best is not present in the Set